Method for producing an mg addition agent



United States Patent C 3,314,787 METHOD FOR PRODUCING AN Mg ADDITION 'AGENT Charles Bruce Goodrich, Charles Ernest Manilla, Cecil Lyle Ramsey, and Richard Herman Hanewald, all of Huntington, W. Va., assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware No Drawing. Original application Mar. 29, 1966, Ser. No. 538,197. Dividedand this application Sept. 8, 1966',Ser.No.-577,806

Claims. (Cl. 75-200) The present application is a division of our copending U.S. application Ser. No. 538,197, filed Mar. 29, 1966.

The present invention is directed to a novel nickelinagnesiumbriquetted agent produced by power metallurgical methods and to the method for producing the said briquetted agent.

The use of various melted and cast alloys containing nickel and magnesium, which are employed industrially as deoxidizing alloys for the treatment of molten nickel and other metals and for the introduction of magnesium into molten cast iron for the production of ductile iron, has long been known. For example, a nickel-magnesiumcarbon alloy having special utility for the purpose of introducing magnesium into molten cast iron is described in U.S. Patent No. 2,529,346 and a nickel-magnesiumsilicon alloy useful for the same purpose is described in U.S. Patents Nos. 2,565,859 and 2,690,392.

range, e.g., inch or inch or larger lumps, has always resulted in the production of a substantial quantity of fine material.

contact with the molten iron with the result that they are ineifecti-ve for the purpose of introducing magnesium in the molten cast iron. Accordingly, these fine materials have been segregated from the desired product and have been remelted to recover the nickel content thereof with accompanying substantial loss of the magnesium content. The production of fines as aforedescribed has resulted in a substantial uneconomic loss of material. Efforts to render the fine material useful for the purpose of introducing magnesiuminto molten cast iron such as be desirable 'to provide an addition alloy containing magnesium which would readily be produced in forms having closely controlled size and which would be more effective for the'pu'rpose of introducing the magnesium 3 content thereof into molten cast iron or into other molten metallic materials. 7

We have now found a powder metallurgical method whereby a nickel-magnesium alloy can be produced without attendant production of fines, which method provides 3,3 14,78 7 Patented Apr. 18, 1967 product having a closely controlled size and shape and having improved utility from the standpoint of increasing the addition efiiciency of the magnesium content thereof into molten cast iron.

It is an object of the present invention to provide a powder metallurgy method for the production of an addition material containing nickel and magnesium.

It is a further object of the invention to provide by powder metallurgy means an addition agent containing nickel and magnesium which provides improved results from the standpoint of is employed for the purpose of introducing magnesium into molten ferrous melts.

Other objects and advantages of the invention a I nickel-magnesium will bea coherent form, perature of at least about 950 F. but not exceeding about 1200 F. in a protective atmosphere, and cooling the sintered material at a rate exceeding about 2 F. minute to provide a sintered agent containing nickel and magnesium, having a porosity of about 20% to about 50%, and an average pore size of about 50 to about 500 microns. The resulting sintered material contains at least about 4% up to about 20% magnesium, e.g., about 207 to about 17% magnesium, has a porosity of about The magnesium into molten cast iron. Advantageously, the sintered briquettes .have a surface area to volume ratio of at least about 8 to 1 when used to introduce magnesium into molten cast iron.

" In preparing the briquetted nickel-magnesium addition material powderhaving exceeding about microns.-

from the standpoint of reactivity, does not exceed about 15%. carbonyl iron,

a particle size not More advantageously, etc, the iron content The iron powder may be reduced iron oxide, etc. It is preferred istics.

Provided the foregoing precautions are observed in the selection of the powder to form the initial powder blend,

it is found that the powder blend presses readily at ambi- V the formation of a porous ent temperatiires to form dense briquettes and other forms which may readliy be handled. The resulting briquettes are then sintered in a protective atmosphere, e.g., hydrogen, argon or other essentiallynitrogen-free atmosphere which will prevent oxidation of the magnesium-bearing briquettes. It has been found that magnesium will form nitrides when heated in a nitrogen-containing atmosphere. These nitrides will react with water vapor to form magnesium oxide and ammonia. The sintering temperature should exceed approximately 950 F. as this is the melting temperature of the lowest melting eutectic formed in the nicke1=ma nesium binary system. A sintering temperature of about 1000 F. is satisfactory. The time of sintering should be sufiicient to cause substantially complete liquid-phase sintering throughout the entire cross section of the briquette. Sintering times of about one to about three hours, e.g., about one hour per inch of cross section, are satisfactory. The sintering operation results in the formation of a liquid phase and sintered structure. It is found that the sintered material should be cooled from the sintering temperature at a rate of at least about 2 F. per minute, e.g., 5 F. per minute or faster, as otherwise cracking of the material sintered at 1000 F. may occur. The sintered briquettes are characterized by high crushing strength, e.g., the briquettes will withstand a compressive tload of at least about 12,000 p.s.i. before crushing. This high strength permits shipment of the briquettes produced in accordance with the invention by usual commercial means without encountering undesirable size degradation leading to the uneconomic production of fines, and accompanying loss of material.

The sintering operation is essential in accordance with the concepts of the present invention in order to provide agents, e.g., bri uetted agents, having the special controlled porosity and quite introduction characteristics when the briquettes are employed for the purpose of introducing magnesium into cast iron. Thus, it is found that when green (unsintered) briquettes, i.e., briquettes which have been formed by isostatic pressing at ambient temperatures, are employed for the aforementioned purpose they have insufficient strength, generate excessive fines during handling, are considerably more reactive in contact with molten cast iron, and give a lower magnesium recovery in cast iron than do briquettes sintered as taught herein. Illustrative data are set forth in Table III hereinafter.

When the briquetted and sintered agents are employed for the purpose of introducing magnesium into molten cast iron by the commonly-employed practice wherein the magnesium-containing agent is placed at the bottom of a ladle and molten cast iron to be treated (at a temperature of about 2500 F. to about 2750" F. or even 2850 F., e.g., 2650 F.) is poured thereover, it is particularly advantageous for purposes of minimizing reactivity to provide the agents in a form which will not float to the surface of the molten cast iron. In order to accomplish this objective, the briquetted and sintered agents are produced in a physical form such that the ratio of surface area to volume is at least 8 to 1. To illustrate the foregoing, a series of sintered 85% nickel- 15% magnesium agents having surface area to volume ratios from 9.5 to 1 to 4.26 to .1 was prepared by mixing fine carbonyl nickel powder with magnesium powder having a particle size in the range minus 20 mesh, plus 70 mesh (Tyler), isostatically pressing the mixture to the various briquette sizes and sintering the resulting briquettes at 1000" F. in hydrogen. The resulting briquettes were then employed to treat 150 pound batches of molten cast iron having the same composition in each instance by ladli'ng the molten cast iron at a temperature of about 2750 F. upon about 1.2 pounds of the sintered briquettes. Data pertaining to these tests are set forth in the following Table I,

TABLE I Ratio Surface Briquette Dimensions Area to Remarks Volume Four pointed star shape inch thic 9.5 to 1 Did not float. Hollow briquette 1 inch diameter x inch 9.4 to 1-- Do.

thick, M inch central longitudinal hole.

1 inch diameter x 0.45 inch thick 8.42 to 1- Do. 0.65 inch diameter x 1 inch thick 8.14 to 1. Do. 1 inch diameter x A inch thick 6.3 to Floated. 1.54 inch diameter x 1.21 inch thick. 4.26 to 1. Do.

An advantageous means for producing briquettes in accordance with the invention comprehends the use of rubber molds wherein the initial powder mix is molded under isostatic pressure to the desired final size having regard for the shrinkage which takes place during pressing and sintering. For example, a plurality of shaped cavities can be punched in a rubber disc having the desired thickness. One end of the cavities can be sealed off by vulcanizing a rubber sheet on one side of the rubber disc to provide a plurality of cup-like cavities in the disc. The disc or a plurality of discs can be filled with powder and stacked in a rubber casing so as to permit isostatic pressing of a number of briquettes simultaneously at a commercial production rate. If desired, billets can be pressedfrom the initial powder mixture and the sintered billet can be crushed to lump form, although this technique provides an undesired loss of material in the form of fines.

In order to 'give those skilled in the art a better understanding of the advantages of the invention, the following illustrative examples are given.

Example I A series of powder blends containing fine carbonyl nickel powder of about 5 micron particle size and magnesium powder of minus 20, plus 70 mesh particle size with hydrogen-reduced iron powder of minus 325 mesh size as an optional addition was prepared and briquettes were pressed isostatically therefrom at about 30,000 psi. pressure using rubber briquette molds. The resulting green briquettes Iwere sintered at about 1000" F. in hydrogen. The resulting briquettes were porous and quite strong in each instance. The compositions of the resulting briquettes are set forth in Table II. In Table II, the briquettes made of alloys 1 through 5 were 1 inch in diameter by about /8 inch thick and had a surface area to volume ratio of about 6.3 to 1 while the briquettes made of alloys 6 through 10 were about 0.65 inch in diameter by about 1 inch thick and had a surface area to volume ratio of about 8.14 to 1.

TABLE II No'rEz-The balance in each case is nickel.

though copper is an undesirable constituent in ductile iron, copper-containing briquettes may be employed in TABLE III Tapping Percent Percent Percent Alloy N o. Tempera- Magnesium Magnesium Magnesium Comments ture, F. Added Recovered Recovery 1n iron 2, 790 0. 076 0. 067 88 Slight floating. 2, 775 0. 077 0. 060 77 Dissolved. 2, 750 0. 095 O. 075 79 Slight floating. 2, 750 0. 135 0. 076 56 Floated. 2, 760 0. 126 0.059 47 Extremely active. 2, 700 0. 139 0. 096 69 Dissolved. 2, 750 O 127 0.072 57. 6 Do. 2, 750 0. 130 0. 071 54. 6 Floated. 2, 700 138 0. 051 37 Do. 2, 700 0 142 0 099 69.7 Dissolved.

1 Green (unsintered) briquettes.

It is to be noted that the green (unsintered) briquette made of the alloy No. 5 composition was extremely active and gave a low magnesium recovery as compared to the sintered briquette made of the comparable alloy No. 4 composition. Furthermore, it is to be noted that the briquettes made of the alloy No. 8 and alloy No. 9 compositions, which contained 20% and 25% iron, respectively, floated and gave materially lower magnesium recoveries than did the briquettes of the alloy No. 6 and alloy No. 10 compositions which contained 10% and 0% iron, respectively.

Example 11 About 30 pounds of nickel-magnesium briquettes containing about 15% magnesium were prepared by isotatic pressing an initial blended mixture of fine carbonyl nickel particle size of pressure. The briquettes in hydrogen and had dimensions of about 0.65 inch diwere poured desulfurization, alloying and other purposes. When the briquettes provided in accordance with the cast iron,

Copper in or about does nat adversely affect the addition char acteristics of the briquettes with respect to cast iron. Al-

treating other types of molten metals. The addition of silicon powder in elemental form to an initial powder mixture results in foaming of the resulting briquettes during sintering. Silicon as a pro-alloyed powder with nickel and magnesium can be introduced into the briquette in amounts up to about 15 or 20% but such an expedient is uneconomic.

pended claims. We claim: 1. The process for producing a briquetted nickel-magnesium addition material which comprises blending fine carbonyl nickel powder with about 4% to about 20% powder having a ing about 2 F. per minute to provide sintered briquettes having a porosity of about 20% to about 2. A process according to claim 1 wherein the magnesium powder has a particle size not exceeding about 1000 microns.

3. A process according to nesium powder has a particle microns.

4. A process according to claim 1 wherein the nickel powder has a particle size not exceeding about 10 microns.

5. A process according to claim 1 wherein the protective atmosphere is selected from the group consisting of hydrogen and argon and the sintering temperature is about 1000 F.

claim 2 wherein the magsize of at least about 200 References Cited by the Examiner UNITED STATES PATENTS 2,726,152 12/1955 Eash. 2,762,705 9/1956 Spear. 3,030,205 4/ 1962 Millis. 

1. THE PROCESS FOR PRODUCING A BRIQUETTED NICKEL-MAGNESIUM ADDITION MATERIAL WHICH COMPRISES BLENDING FINE CARBONYL NICKEL POWDER WITH ABOUT 4% TO ABOUT 20% BY WEIGHT OF MAGNESIUM POWDER HAVING A PARTICLE SIZE OF AT LEAST ABOUT 40 MICRONS, AND UP TO ABOUT 25% OF IRON POWDER HAVING A PARTICLE SIZE NOT EXCEEDING 150 MICRONS, COLD PRESSING THE MIXED POWDERS TO GREEN BRIQUETTES, SINTERING SAID GREEN BRIQUETTES BY HEATING FOR ABOUT ONE TO ABOUT THREE HOURS AT A TEMPERATURE NOT EXCEEDING ABOUT 1200*F. BUT SUFFICIENTLY HIGH TO FORM A MOLTEN PHASE THEREIN AN ESSENTIALLY NITROGEN-FREE PROTECTIVE ATMOSPHERE AND COOLING THE SINTERED BRIQUETTES AT A RATE EXCEEDING ABOUT 2*F. PER MINUTE TO PROVIDE SINTERED BRIQUETTES HAVING A POROSITY OF ABOUT 20% TO ABOUT 50%. 